1. Field of the Invention
The present invention relates to a scanning exposure method and scanning type exposure apparatus which move a mask and a substrate in a synchronous manner in a predetermined direction, and conduct the scanning exposure of a pattern formed in the mask onto a substrate such as a glass substrate or the like.
2. Description of the Related Art
In recent years, liquid crystal display panels, which make it possible to make personal computers and televisions and the like thinner, have come to be employed in a variety of ways as the display elements of such devices. This type of liquid crystal display panel is manufactured by patterning transparent thin film electrodes on a planar rectangular photosensitive substrate into a desired pattern using photolithography. An exposure apparatus which exposes a pattern formed on a mask (reticle) onto a photoresist layer on a photosensitive substrate via a projection optical system is used as an apparatus for this photolithography.
Liquid crystal display panels have increased in surface area in order to improve the viewability of the screen. A scanning type exposure apparatus has been proposed as an exposure apparatus capable of meeting these needs; such an apparatus, as disclosed, for example, in Japanese Patent Application, first publication No. HEI 7-57986, combines a plurality of projection optical systems which project the mask pattern onto a substrate as a positive image, moves the mask and the glass substrate in a predetermined direction in a synchronous manner, and conducts scanning with respect to the projection optical systems, and thereby successively transfers patterns having a large exposure region in a direction perpendicular to the direction of synchronous movement, that is to say, the patterns of LCD (liquid crystal displays) formed on the mask or the like, to the exposure region on the glass substrate.
At this time, so that the apparatus size does not increase even as the projection region increases, and so that satisfactory image formation characteristics are obtained, the projection optical system employed is one in which a plurality of projection optical systems are disposed in such a way that the ends of adjoining projection regions overlap in a direction perpendicular to the direction of scanning, so that the adjoining projection regions are displaced by a predetermined amount in the direction of scanning. In such a case, the field diaphragm of each projection optical system is platform-shaped so that the total opening width of the field diaphragm in the direction of scanning is always the same. For this reason, in a scanning type exposure apparatus such as that described above, the junction parts of adjoining projection optical systems overlap and are exposed, and this is advantageous in that the optical aberrations or exposure intensity of the projection optical systems can be smoothly altered.
In recent years, the use of large glass substrates of approximately one square meter as substrates for producing liquid crystal display panels has been contemplated in order to increase throughput by producing multiple liquid crystal panels, or in order to produce liquid crystal display panels having larger display regions in order to create televisions.
In this way, in order to expose a liquid crystal display panels having a substrate size corresponding to a large display area, a method has been considered in which a mask having a size equal to the substrate is employed and scanning and exposure are conducted all at once, and a method has been considered in which the pattern is formed while dividing the pattern of a single liquid crystal display panel into a plurality of regions. By using the former method, high-speed throughput becomes possible; however, the cost of the mask becomes excessive, and the method is not practical.
On the other hand, when the latter method is employed, misalignments occur as a result of mask pattern drawing errors at the pattern junction parts, optical aberrations in the projection optical system or positioning errors of the stage which moves the glass substrate, and there are cases in which the device characteristics are negatively affected. Furthermore, when a number of such patterns are overlaid on one another, errors in the overlaying of the exposed regions and differences in linear width in the patterns change in a discontinuous manner at the junction parts of the patterns, and when the liquid crystal display panel is engaged, color irregularities and the like are produced at the junction parts, and the quality of the device declines.
A standing type exposure apparatus for exposing a large glass substrate which attempts to solve these problems is disclosed in, for example, Japanese Patent Application, first publication No. HEI 10-64782. In this apparatus, a mask stage which supports the mask and a substrate stage which supports the glass substrate are driven in a synchronous manner and scanning and exposure is conducted, and thereafter, step movement of the mask stage and the substrate stage is conducted in a direction perpendicular to the direction of synchronous movement by a distance corresponding to the width of the illuminated region, and this process is repeated once or a plurality of times, and thereby a plurality of separate patterns are connected and transferred onto a large glass substrate.
However, the conventional scanning exposure methods and scanning type exposure apparatuses described above have the following problems.
The LCD patterns described above comprise picture element parts which are formed with a pattern in which a plurality of electrodes corresponding to a plurality of pixels are systematically arranged, and conducting parts which serve to electrically connect the pattern of the various electrodes of the picture element parts and the driver circuits which drive these electrodes, are present. These picture element parts are formed in the various connected partial patterns on the glass substrate by the scanning type exposure apparatus described above.
However, in the scanning type exposure apparatus described above, the contents of the mask pattern are not considered, and the mask pattern is simply divided and transferred to the glass substrate, so that the mask may have a size which is equal to that of the glass substrate or may be larger than the glass substrate. For this reason, in addition to the increasing cost of the mask, it is necessary that the stage which supports the mask have the same size as the mask, and this contributes to an increase in size in the apparatus and to an increase in costs.